1. Field of the Invention
The present invention relates to a stable m-vinylphenol composition, and methods of stabilizing and purifying m-vinylphenol.
2. Description of the Background Art
m-Vinylphenol is useful as a monomer for producing homopolymers and copolymers having hydroxyl groups in their molecules. Besides, the thus-obtained homopolymers and copolymers having hydroxyl groups in their molecules are rich in reactivity and are hence substances useful in various fields.
However, m-vinylphenol is very unstable compared with vinylbenzene and hence involves a drawback that it tends to cause a polymerization reaction during its handling or treatment such as storage, shipment or purification. In particular, such tendency becomes pronounced at a high temperature. It is therefore necessary to keep m-vinylphenol stable so as not to cause a polymerization reaction upon its handling or treatment such as storage, shipment or purification.
Thus, many investigations as to the inhibition of polymerization of vinylphenols (ortho, meta and para isomers) have heretofore been made. For example, there have been proposed a method in which an alcohol having or not having a substituent group or a phenol having or not having a substituent group is added as a polymerization inhibitor (Japanese Patent Publication No. 29137/1976), a method in which an aromatic nitro compound or a sulfoxide is added as a polymerization inhibitor (Japanese Patent Publication No. 41577/1979), a method in which an ether, a ketone or a sulfone is added (Japanese Patent Publication No. 16129/1980) and a method in which a nitrile is added (Japanese Patent Publication No. 24771/1982). Concerning the inhibition of polymerization of m-vinylphenol, it has also been proposed to add an aliphatic amine such as trimethylamine, an aromatic amine such as o- or p-phenylenediamine or aniline, a heterocyclic amine such as pyridine, quinoline or piperidine, phenylhydrazine, or the like (U.K. Patent No. 670,502). All these various compounds used as the polymerization inhibitors for vinylphenols or m-vinylphenol have been insufficient in the polymerization-inhibiting effect and hence not satisfactory.